The present invention relates to the field of high pressure connectors for hydraulic lines. More particularly, the invention relates to a hydraulic conduit connector having backup seal and test capabilities for preventing intrusion of highly pressurized fluids into the hydraulic conduit interior.
Hydraulic conduits or lines are installed in hydrocarbon producing wells to provide hydraulic power for operating downhole well equipment. High pressures and temperatures of the external wellbore fluids require hydraulic line connectors resistant to failure. The connectors should withstand wear, temperature expansion and temperature cycling without permitting intrusion of external wellbore fluids into the hydraulic lines, or of escape of hydraulic fluid into the wellbore. The connectors must also withstand vibrations induced by high pressure gas flow or liquid flow past the tubing exterior surfaces. In standard connection systems, bending stresses on tubing imposed by excessive vibration may cause premature fatigue tubing failure. Although tapered seals and gland nuts have been used to move the stress concentration to unthreaded tubing sections, such vibration resistant connections do not provide fluid tight seals.
Various connectors provide fluid tight seals between tubing and downhole well tools. Conventional hydraulic connector attach tubing to an oversized plug. The plug is attached to a compression nut, and a ferrule provides metal to metal contact between the plug and the compression nut. The compression nut is substantially larger than the tubing, and the bushing, ferrule and multiple seals can fail under high pressure. The overall plug dimension for this connector is long when compared to the tubing diameter, and such configuration effectively prevents the connection from being positioned transversely in a confined space such as a downhole well casing. This oversize dimension is also undesirable because the connector creates an additional obstruction in the well.
Various efforts have been made to overcome limitations of conventional connectors. For example, U.S. Pat. No. 4,553,776 to Dodd (1985) disclosed a high pressure connector for attachment to a small diameter tubing. A first locking nut compressed a packing gland and metal packing rings with a body element recess, and a second packing nut compressed metal ferrules to connect the first tubing end to the first locking nut. Although four sealing surfaces were created by this configuration, the interdependency of the sealing elements required precision machining for each component. The connector cannot fit within narrowly confined spaces and is expensive to manufacture. Slight machining errors, subsequent damage to the sealing components, or improper assembly of the components can cause failure of the connection because of the limited design tolerances.
Another limitation of conventional tubing connections is the inability to effectively test the connection before the tubing connection is installed in a remote location such as a wellbore. After the connections are made up, the entire line must be pressure tested to verify the absence of tubing fluid leaks. Convenient techniques for pressure testing a single connector are not easily performed in a field environment.
Accordingly, a need exists for an improved high pressure hydraulic line connector providing a seal system capable of withstanding high fluid pressures and temperatures. The connector should not create obstructions within enclosed spaces, should be sufficiently short to permit transverse well connections, and should permit pressure testing of the connector before the connector is installed in the well. The connector should also be capable of handling long tubing strings and should withstand fluid flow induced vibration forces acting on such tubing.